Extract data from a .mat file entred by the user

Hello team !

So i am making an app, where the user can load a .mat file of diffrent driving profiles. This means that the user file name can be anything. so we can not specify the name of the file to be loaded and use just

load('WLTC_Driving_Cycle.mat')

So the idea is, to use fileName to get the name what ever is the name of the .mat file, and then load it. here is my code

fileName = uigetfile('*.mat');     % Open window to select .mat file and get the name of the file
load(fileName)                     % Load the file

Speed = fileName.Data;             % << The problem is here, dot call can not be used since "fileName" is char, so i cant import de the data
% Extract Data from the file

for i= 1 : length(speed)           
    s(1,i) = i-1;                 % time (s)
    s(2,i) = speed(i);            % Extract speed
end

As we can see, i am not sure how to extract the data from the file, one idea is to do this :

temp = load(fileName)
speed (1,:) = temp.fileName.Data        % Matlab Throws an error since he considers fileName is path to get data

Answer 1

[Stephen Cobeldick]

"...one idea is to do this "

You just need to use dynamic fieldnames:

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

S = load(...);
S.('somefield')

You can get the fieldnames contained in the structure using fieldnames:

https://www.mathworks.com/help/matlab/ref/fieldnames.html

Note that your examples (in your question and various comments) do not reflect the content of the mat file, which contains three scalar structures, none of which have a Data field (all three have the same two fields: MCOS and timeseries).

[Cris LaPierre]

Data is a property of the timeseries object.

Assuming the *.mat file only has a single variable in it, do the following

fileName = uigetfile('*.mat');
S=load(fileName);
fn = fieldnames(S);
speed = S.(fn{1}).Data

[Stephen Cobeldick]

Or, again assuming only one variable per file:

C = struct2cell(load(filename));
speed = C{1}.Data;